My "identity-based" here includes your "personalities/identities/parties". I complained about this before: American election politics is becoming too much like a sport. Supporters/voters fight so hard not because they are so divided on issues, it's because of their supported identity (person, party). This identity is their team and their team has to win, beat the other team, regardless of the issues. So, the politics, to most people, is identity-based politics, not issue-based politics.
I am just imaging what if R and D merged into one party - one identity. So, all voters are one-identity supporters. Voters will still be divided on candidates, but this division is much more issue-based. It's like fans debated on who should start as QB, Crist or Rees. Our focus is more on football issues related to these 2 QBS, not other things. And our difference and debate are much healthy because we are all one-identity, Notre dame football supporters.